Selective signal system



Jan. 25, 1938. J. C. FIELD SELECTIVE SIGNAL sYsTEM Filed March 11, 1936 INVENTOR J CTF/ELD a w: R Q

A TTORNE Y Patented Jan. 25, 1938 2,106,498

UNITED STATES PATENT OFFlQE SELECTIVE SIGNAL SYSTEM Joseph 0. Field, Maplewood, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 11, 1936, Serial No. 68,232

2 Claims. (01. 177-342) This invention relates to signaling systems and nected in parallel and in circuit with the local more particularly to signaling systems provided battery 88 and are controlled by the impulse with answer-back signaling means. transmitters 89, 99, 9i, 92 and 93. These trans- The object of this invention is to provide mitters may be variously adjusted for selectively answer-back signaling means comparatively low operating individually or collectively the several in cost and which may be used in combination selectors connected with the line or to operate a with a selective signaling system. single selector for selectively closing any one A feature of this invention resides in means of a plurality of contacts corresponding to any provided for establishing an inductive coupling one of the signal bells 16 associated with the par- 10 betweenalocal circuit, including signaling devices, ticular selector. These transmitters, as clearly and the line circuit of a signaling system. described in Patent 1,306,054 are provided with Other features residing in the particular form teeth, certain ones of which may be blocked out and arrangement of the parts in the circuit will by one or both adjustable cams 99 and 95 to obbe subsequently pointed out in the specification. tain a particular number and combination of The invention may be used in connection with effective teeth for calling purposes. Each trans- 15 a selective signaling system of the type in which mitter is adapted to rotate in the direction of the selectors at way stations are operated under the arrow and the teeth thereon are provided to control of sending apparatus at a central stathrow contact springs 96 and 91 in circuit with the tion. The drawing shows the invention applied pole-changing relay 81. The free end of contact to asystem of the type above mentioned and emsprings 9'l of transmitters 89 and 99 is bent 20 b-odying apparatus fully described in Patent downward and carries at the extreme end there- 1,343,256 of June 15, 1920, to which reference may of an insulating roller 98 which as the transmitter be had for a full detailed description of the way rotates is adapted to ride on top of the cam. 95 station apparatus disclosed in this application, and separate contacts 96 and 9? during the time .25 while the sending key apparatus disclosed is fully of the passage of cam 95. Assuming that trans- 5 described in Patent 1,306,054 of June 20, 1919. mitter 89 is operated, it will be noted that as the The drawing discloses a selective signaling sysdisc thereof starts to rotate the circuit of relay tem to which may be connected a large number of 86 is completed, operating the relay and connectway stations, at each of which is a selector selecing battery 89 to the line wires. As contact tively responsive to a definite combination of spring 96 rides upon the first tooth, it also en- 30 code impulses, but for convenience of illustration gages spring 91 to actuate the pole-changing reonly two way stations are shown. lay 8? by current from battery 98, thereby re- In the drawing, l9 and H designate line wires versing the connection of battery 86 to the line extending from a central transmitting or diswires. When the spring 96 drops between two patchers station A to a plurality of receiving or adjacent teeth, relay 9? will be deenergized and 35 way stations B and C. At each way station is a during the e Sp 96 is passing over the selector designated generally as 12, the energizcam 99, relay 81 will be energized to furnish a ing windings 5, 5 of which are connected in bridge prolonged impulse of one polarity, for example, of the line wires and in series with a condenser negative. As the disc continues to rotate, alter- 14 and two impedance coils l5, 15. Each way nating impulses are sent over the line andwhen 40 station is also equipped with a plurality of signal the cam 95 is reached, the insulating roller 98 bells 16 under control of the selector thereat and on the spring 97 rides thereon and raises spring a telephone set Tl included in a normally open 91 to keep it out of reach of spring 96 so that bridge of the line wires. A single battery 18 during the time that the insulating roller 98 is at each way station may serve for operating any riding over cam 95 a prolonged impulse of op- 45 one of the signal bells l6 and for furnishing curposite or positive polarity is sent over the line rent to the telephone set for talking purposes. wires. As the disc continues to rotate, additional At the transmitting station A there is a main alternating impulses are sent out over the line battery 85 for supplying current for operating the Wires and when the spring 96 rides on the cam selectors at the way stations. This battery is surface I99 a prolonged impulse is sent over the 50 normally disconnected from the line wires and line wires to provide a ringing period. When the may be connected therewith by the operation of a spring 96 drops on the cam surface It! a prorelay 86. A pole-changing relay 8! is provided longed positive impulse is sent over the line wires for reversing the connections from battery 85 to to release the selector at the selected station.

the line wires. The relays 86 and 8'! are con- When spring 96 is out of engagement with the 55 toothed wheel, relay 86 is released and battery is disconnected from the line.

Now assume that the selector at way station B is arranged to respond to a code of impulses represented by 39-3 to close the local circuit for the first bell of the series 16. When the transmitter 89 is operated, it will first complete a circuit for relay 86 to connect battery 85 to the lines 78 and II. The circuit is completed by the engagement of the toothed wheel with the spring 96. When the battery 85 is brought into connection with the line wires 18 and II an impulse of current flows to the selectors I2 at the way stations. The selectors, therefore, move one step but since the contacting portion of the toothed wheel, preceding the first tooth, is comparatively long the selectors restore to normal position again. The toothed wheel continues to rotate and then alternately closes, opens and closes, through springs 96 and 91, the circuit of relay 81. Since relay 81 operates as a pole changer for the battery 85 three impulses of opposite polarity are sent to the selectors at the way stations. The third impulse by reason of the length of the cam 94 is of sufficient duration to permit the magnets of all selectors on the line to release before the first impulse of the second set is sent. It should be understood that when potential of either polarity is applied to the line for a suificient interval the condensers I4, I4 become charged whereupon the flow of current through the selector magnets ceases and the selector magnets release. Those selectors, including the wanted station B, arranged to respond to codes of impulses the first set of which is made up of 3, will, in releasing, cause the curved end 38 of the contact springs 35 to engage the holding pin 21 in the contact carrying member 28, so that the contact carrying members 28 at these particular stations will be held in advanced position. All other selectors on the line, including the one at station C, requiring a different number of current impulses to bring their pins 2! into engagement with the curved end 38 of spring 35 will be dropped back to normal position. Nine impulses will next be transmitted over the line to step the ratchet wheel ll around to a position where, when the selector magnets are deenergized, due to the extended duration of the ninth impulse, curved end 38 of spring 35 will engage the pin 28 at station B, thus holding the selector at that station in advanced position, while the selector at station C will return to normal position. The selectors at all stations connected to the line, which are arranged to hold in response to a code of impulses, the sum of the impulses of the first two sets of which total nine, and those arranged to hold in response to a code of impulses, the first set of which is of nine impulses, will also be held in advanced position, while all other selectors, which were held in advanced position at the end of the first set of impulses transmitted, will be returned to normal position. Three impulses now sent over the line circuit will cause the engagement of contact 2| with the contact 22 at station B, and the engagement of curved end 38 of spring 35 with holding pin 29. The stopping of contact 2I on contact 22 closes an energizing circuit through the energizing winding I85 of a relay I86, the operation of which closes contacts I88 on the relay I86.

Relay I86 has two windings on the same core, one of them being the relay winding I85 and the other being a winding III which is included in a normally open bridge across the line wires I8 and II, the windings being inductively associated to form an inductive connection between the local circuit including the signal bells I6 at the way station and the line circuit leading to station A. When contact 2I of the selector I2 comes to rest on contact 22 and is retained thereon by reason of the holding of the contact carrying member 28 in advanced position by engagement of the curved end 38 with holding pin 29, relay I86 is energized over a circuit which may be traced from battery I8, conductor I9, energizing winding I85of relay I86,conductor I I 8,break contacts H2 of bell signals I6, conductor 8|, contact 22 of selector I2, contact 2|, contact carrying member 28, holding pin 29, spring 35, conductor H3 to battery I8. The extreme righthand bell of the signal bells I6 is operated over this circuit and intermittently breaks and closes the circuit through its break contacts I l2. When relay I86 is energized it closes contacts I88 and connects the secondary winding II! on relay I86 across the conductors I8 and II of the line circuit. The connection of secondary winding III across the line circuit may be traced from line Wire I8, conductor II5, condensers H6, in parallel, contacts 188, secondary winding III, conductor II9 to line wire II.

Now, as the signal bell I6 vibrates in response to the current from battery I8 and intermittently opens and closes its energizing circuit the pulsations will pass through winding I85 of relay I86, thereby inducing current into winding II! on the relay I86. The current pulsations induced in the winding II! will pass over the line wires I8 and II to a receiver I28 in permanent bridge of the line wires I8 and TI at the dispatchers station A and these pulsations will generate a tone in the receiver I28 which will indicate the operation of the signal bell 76 at the selected way station.

To prevent relay I86 from being deenergized at each break of the break contacts l'l2 a holding circuit for relay I86 is provided. The holding circuit may be traced from battery I8, conductor I9, winding I85 of relay I88, conductor H8, conductor I28, resistance I2I, conductor I22, contact carrying member 28, holding pin 29, spring 35, conductor II3 to battery 78. Resistance I2I is of sufficiently high value to make the current for energization of relay I86 normally pass over the circuit including the break contacts of the signal bells I6 but when the break contacts of the signal bells I6 are intermittently opened sufiicient current will flow in the holding circuit to prevent deenergization of relay I86. This prevents chattering of the contacts I83 under all conditions of operation. The answerback signals, therefore, are not changed or interfered with by contacts of the relay I86.

The windings I85 and I I! on the core of relay I86 are preferably arranged to produce a stepup transformer effect, the step-up being from the energizing winding I85 of the relay I86 to the inductively associated winding III which when contacts I88 are closed is bridged across the line wires I8 and II.

The signal bells I6, obviously, may be located at various positions remote from each other and may serve as signal devices for stations served by the common selector I2, the selector operating to select a required station in accordance with the code signals sent from station A. Each bell is connected to a separate fixed contact on the selector I2 and maybe separately brought into Operation by movement of the selector contact 2! to the required fixed contact. One terminal of the extreme right-hand signal bell I6 is connected by means of conductor 8I to the terminal 22 of the selector. The other terminal of this bell is connected to conductor IIO which is in the normal energizing circuit of relay I06. Conductor H is common to all of the signal bells I6 in the set. The bell next in line, to the extreme right-hand bell, is connected by means of conductor 82 to contact 23 of the selector I2. The next bell is connected by means of conductor 83 to contact 24. The left-hand bell is connected by means of conductor 84 to contact 25. By sending a required number of impulses from station A to the selector at the way station any one of the signal bells I6 may be selectively brought into operation.

Since the signal bells I6 are included in a local circuit which is normally open and which is not closed until the selector I2 has operated to a holding position where the spring 35 engages a holding pin and since the relay I06 does not operate to close contact I08 until the holding position has been reached by the selector and the selector has stopped in its selective operation there is no likelihood that a false signal will be given either at the way station or in the form of an answer-back tone to the station A. Also, a relay with the inductively associated windings as described provides a comparatively low cost inductive apparatus and also makes it.

possible to use comparatively low cost signal bells or buzzers in the local circuit.

When the selector I2 is operated to move the contact 2I to one of the fixed contacts beyond contact 22, that is, to contacts 23, 24 or 25, there is no operation of the bell signals 16 or closing of contacts I08 as the contact 2| passes across the preceding fixed contacts of the selector. The reasons for this are that these contacts are passed quite rapidly and the circuit for energizing the signal bells I6 and the relay I06 is not made by the engagement of the hooked end 38 of spring 35 with a holding pin on the contact carrying member 20 until the selector has stopped in its advance movement. When the selector stops advancing, a return spring in the selector moves the contact carrying member in reverse direction to a slight extent and spring 35 is moved so that the curved end 38 comes into the pathof movement of the nearest holding pin. The spring 35 as explained in the above-identified patent covering the selector does not come to a rest position where the hooked end 38 will engage a holding pin until the electromagnets of the selector are deenergized.

What is claimed is:

1. A signaling system comprising in combination, a line circuit, a selector controlled over said line circuit, a local circuit controlled by said selector, a signaling device in said local circuit, said signaling device being of the self-interrupting type and having normally closed contacts in said local circuit operated by said signaling device, a relay having its operating winding in said local circuit, a normally open bridge across said line circuit, a winding in said normally open bridge, said winding being inductively associated with the operating winding of said relay, contacts in said normally open bridge, said contacts being controlled by said relay to establish an inductive connection between said local circuit and said line circuit, and a holding circuit for said relay comprising a resistance in shunt of said signaling device to hold said relay operated during the open periods of the contacts operated by said signaling device.

2. In a signaling system in combination, a line circuit, a selector connected to said line circuit, a local circuit, normally open branches in said local circuit, a signaling device of the self-interrupting type in each of said normally open branches, contacts in said normally open branches selectively closed by means of said selector, a relay having its operating winding in said local circuit and common to said normally open branches, said relay being energized when any one of said branches is closed, a normally open bridge across said line circuit and closedby means of said relay and a coil in said normally open bridge in inductive relation with the operating winding of said relay and forming an inductive connection between said local circuit and said line circuit when said normally open bridge is closed.

JOSEPH C. FIELD. 

